Brake Pedal Feel

[RDKeysor]

Replaced my '60 BN7 master cylinder a couple of months ago with a standard 5/8" bore type as used on the Series 1 cars without servo. I also switched to NAPA Dot 4. Even though I bled the system thoroughly, I had maybe 2" of pedal travel before I got braking, the pedal firm at that point. The other day a front wheel cylinder failed, so I purchased rebuild kits and new pistons (the ones in the car had a chrome look and corrosion rings with some pitting about where the inner rubber seals contacts them). Since I had a lot of previous recommendations that I replace the rubber hoses with the stainless steel mesh type, I bought the set from Moss and installed them, front and back, along with the new pistons and rebuild kits. However, I still have the same long pedal travel before getting my hard pedal, and that distracts from any benefit I might have had from the new brake hoses. I'm considering buying the 7/8" bore master cylinder specified as being for cars with servos thinking that the larger diameter will move more fluid and eliminate the long pedal throw. I own a complete servo kit that I have been reluctant to install until I am satisfied with the function of the system without the added complexity. I might add that I recall the pedal travel as being shorter before I began this process, which was occasioned by the large amount of crud in the brake fluid. It comes out crystal clear now, and I have put a lot of it through the system. Thoughts?

 

[bdcvg]

I don't think the larger diameter equals less pedal travel. My BJ8 was converted from large servo master to smaller non-servo BJ7 master plus braided lines and there is much less pedal travel now.

 

[vette]

I'm not an expert in hydralics and such, but even in reading about hot rod build projects I believe that the smaller diameter master cylinder contributes to more pressure which is better than more volume. I might be wrong. I know I have always found it difficult to get a good bleed on my BJ7 brakes. I do believe that it is because of the smaller size of the bore of the Master Cylinder. As said earlier, it doesn't move much fluid so when trying to move the air out of the system it takes alot of time (when using the pump the pedal method). But once the system is bleed up, VERY WELL, I believe the smaller bore master cylinder contributes to a harder pedal.

 

[Gearhead_Garage]

I finally received my stainless lines from England (motorsport-tools.com). They are stainless coated with a dark transparent sleeve, sort of half-way between rubber and stainless. They look stock until you look closer.

They took forever to arrive but they sure are purty. I could have had the Moss or Goodridge lines installed by now but sometimes you just want to give your Healey a new toy.

I am renovating the shop so no car work until it is finished. I'll report back on a before/after.

 

[RDKeysor]

Coincidental to my brake issue, I think I have confirmed to my own satisfaction Norman Nock's "Tech Talk" observation that Healey's don't respond well to pressure bleeders, in my case a Mighty Vac (sic). I had tried this on two occasions and kept getting air bubbles, but when I then used the two-man bleeding system, I quickly got clear fluid. I have a Motive (sic?) pressure bleeder, the type that holds brake fluid and pressurizes at the reservoir. This works well on my Porsche 968, but these things are specific to the brake fluid reservoir cap/threads. Don't have the Healey cap fitting. I will be curious about observations on vette*'s comment regarding cylinder diameter and hydraulic response. I know zilch about that but remember well that four 1" water line capacity doesn't compare to one 4" line. Just trying to further confuse the issue!